During the life of the aircraft, a panel made of laminated composite material used to produce a fuselage or a wing element undergoes impacts on its free face, also called a front face, as a result of, for example, collisions with birds, or from tools dropped during maintenance operations. The panels made of laminated composite materials are produced by a stacking of a plurality of layers, formed from fibers, held together by means of a hardened resin. The impacts on the free face of the panels degrade the structure of the panel because they cause delaminations between its layers. However, a simple visual inspection is often not sufficient to detect delaminations in the panels. Accordingly, devices are needed to inspect the panels for delaminations.
EP1759195 describes an ultrasound detection device for revealing whether delaminations are present in the thickness of a panel, following an impact. This device sends, via a probe in contact with the front face of the inspected panel, an ultrasound pulse. The device also collects the pulse reflected by the back face of the panel. The device then compares a form and a turnaround time of a signal, called reference signal, reflected by the back face of the panel obtained when the panel is healthy. A difference in form and turnaround time between the two reflected signals beyond acceptable limits reveals a delamination.
The device of EP1759195 requires, prior to use, a calibration on a healthy panel having the same dimensions as the panel to be inspected in order to obtain a form and a turnaround time for the reference signal. As a result of this calibration, this device is very effective for inspecting panels that have a constant thickness, however the device provides inaccurate results when the probe is moved over a length of a panel which exhibits a changing thickness along its length. Currently, the fuselage and/or the wing elements of many aircraft are formed with laminated composite panels having a non-constant thickness. Thus, the device of EP1759195 cannot be used accurately on such aircraft.
To overcome the shortcomings of devices like those in EP1759195, the applicant of the present application has previously provided a method and device to inspect such panels with non-uniform thickness. Specifically, U.S. Pat. Pub. No. 2015/0160166, the entirety of which is incorporated herein by reference, discloses a device which indicates delamination on panels having a non-constant thickness. Additionally, the device does not require an initial calibration on a healthy panel. However, while effective for its intended use, when the device disclosed in U.S. Pat. Pub. No. 2015/0160166 is used to inspect panels, the operator is required to analyze the panel and estimate the dimensions of the detected delamination. In other words, the device does not provide dimensions of the detected defects via a non-destructive ultrasound inspection process.
Therefore, the present invention is directed at remedying some or all of these shortcomings and making it possible to detect a defect and provide a dimension to this defect automatically and accurately via a non-destructive ultrasound inspection process.